SANITATION AND HYGIENE ON TROPICAL ESTATES 93 



thoroughly within a distance of half a mile of a dense 

 population, although a less distance will give adequate 

 protection to a scattered population, and local circum- 

 stances must be considered in this connection. From the 

 rate per acre given above the approximate cost of an 

 anti-malarial drainage scheme in any locality can easily be 

 obtained by those having a full knowledge of local con- 

 ditions. A close estimate of the cost of any particular 

 works can only be prepared by an engineer who has had 

 experience of the work required. One point needs special 

 consideration in any scheme for thorough drainage as an 

 anti-malarial measure, and that is, whether it is better to 

 concentrate the population it is desired to protect or to 

 protect it in a scattered condition. There can be no 

 doubt that at least partial concentration is economical, 

 and the cost, il any, of moving buildings on this account 

 should be added to the cost of the drainage scheme to 

 obtain the total cost. No difficulty can attach to concen- 

 tration of population either in a town or on most agricul- 

 tural estates, but further experience is needed before a 

 pronouncement can be made in connection with areas 

 under rice cultivation and other similar areas. 



Against the expenditure on thorough drainage has to be 

 set the great improvement to health conditions which 

 will undoubtedly follow, and in particular on estates, in 

 which this Congress is interested, the greater working 

 capacity of the labour force, the greater efficiency of the 

 labour force consequent on better management resulting 

 from more active supervision on the part of a healthy 

 manager and assistants, reduction in recruiting ex- 

 penses due to improved reputation, and reduction 

 in medical administration charges. The greater working 

 capacity and efficiency of the labour force following 

 improved health conditions will usually be the most 

 important, although there are many estates in the Malay 

 States where the reduction in medical administration 

 charges alone, if malaria were eliminated, would pay 

 for a thorough drainage scheme in about three years, 

 and these are by no means the worst cases. The differ- 

 ence in cost of labour per unit of output from a well and 

 a badly managed labour force can easily amount to 50 per 



